An antenna is a medium for radiating and receiving electromagnetic waves. Over the years, the design and performance of antennas for wireless communication devices has gained significant importance. Key technological aspects involved in the development of an antenna for a wireless communication device include compactness of the antenna, complete built-in structure of the antenna, and multi-band operation of the antenna.
To efficiently radiate an electromagnetic wave into free space, the size of the antenna should be of the order of the wavelength radiated, which is inversely proportional to the frequency. For example, a wavelength at 900 MHz, used in the GSM system, is 330 mm, which is much larger than the size of wireless communication devices currently in use. Generally, the operational frequency of a wireless device has a long wavelength relative to the size of the handset. In particular, the terms ‘compact size’ and ‘broad bandwidth’ generally conflict with each other. Therefore, the design of an antenna embedded in a wireless communication device should be small yet should handle frequencies that generally require larger antenna dimensions.
In contrast to external antennas, complete built-in antennas are installed within a housing of a wireless device. The advantages of a complete built-in antenna include reinforcement of shock resistance, consistent antenna efficiency, reduction of manufacturing costs, etc. Therefore, requests for complete built-in antennas for wireless communication devices are growing.
A multi-band antenna is one that can be used in more than one frequency band. There are different communication protocols utilizing different frequency bands. Examples of communication protocols include AMPS, GSM 800, GSM 900, GSM 1800, GSM 1900, and UMTS. It is desirable that wireless communication devices that are capable of operating according to more than one communication protocol are produced. This may necessitate signals being radiated and received in different frequency bands.
Therefore, there is an opportunity to develop compact-sized internal antennas, capable of operating in multiple frequency bands (rather than with separate antennas for different bands).
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of the embodiments shown.